Drill string shock absorber and vibration dampener



F. K. FOX

Jan. 25, 1966 DRILL STRING SHOCK ABSORBER AND VIBRATION DAMPENER Filed 001;- 16, 1963 4 Sheets-Sheet 1 INVENTOR.

Free FOX Jan. 25, 1966 F. K. FOX 3,230,740

DRILL scram; sHocK ABSORBER AND VIBRATION DAMPENER Filed Oct. 16, 1963 4 Sheets-Sheet 2 F/ e 0 K F 0 x INVENTOR.

Jan. 25, 1966 F. K. FOX 3,230,740

DRILL STRING SHOCK ABSORBER AND VIBRATION DAMPENER Filed Oct. 16, 1963 4 Sheets-Sheet 5 IN VEN TOR.

ATTU/P/VEYJ F. K. FOX

Jan. 25, 1966 DRILL STRING SHOCK ABSORBER AND VIBRATION DAMPENER Filed 001;. 16, 1963 4 Sheets-Sheet 4.

United States Patent 3,230,740 DRILL STRING SHGCK ABSORBER AND VIBRATEON DAMPENER Fred K. Fox, 242 Stoney Creek Drive, Houston, Tex. Filed Oct. 16, 1963, Ser. No. 316,729 17 Claims. (Cl. 64-23) This invention relates in general to a device for cushioning shocks and vibrations upon the drill string and bit in the drilling of a well. More particularly, it relates to an improved device of this type which is connectible in a rotary drill string useful in the drilling of oil and gas wells in which a drilling mud is circulated through the drill string and bit.

One of the more serious problems resulting from the shock and vibration encountered in the rotary drilling of oil and gas Wells is the wear on the rotating cones of the bit. This same shock and vibration can also be harmful to the drill collars and joints of drill pipe above the bit, particularly the threaded connections between them. These problems become more serious as the drilling proceeds, because the formation generally becomes correspondingly harder.

In a prior device of this general type, a heavy rubber sleeve is vulcanized to relatively movable tubular parts of the drill string so as to cushion torsional as well as cornpressive loads. However, the use of this device is limited not only by the fatigue of the rubber, but also by bottom hole temperatures which generally rise as a well is drilled deeper. Also, of course, when the rubber sleeve is replaced, the device must be taken to the shop.

In another device of this general type, a jet nozzle is disposed within the bore of one of a pair of relatively movable tubular parts of the drill string so as to create a dif- -ferential pressure across the upper end of the one part. Although this provides a downwardly directed force for cushioning compressive loads on the bit and drill string, this force is limited to the pressure drop created across the jet nozzle. Furthermore, since less pressure drop is available as the well is drilled deeper, the available cushioning force will actually decrease as the need for same becomes greater. Still further, the use of the jet nozzle within the cushioning device necessarily deprives the bit of a jetting action which would increase its drilling efficiency.

An object of this invention is to provide a device of this general type which is not subject to the above-noted shortcomings.

A more particular object is to provide such a device which, as a practical matter, is not limited in its use by bottom hole temperature.

Another object is to provide such a device which has a long, useful life, which seldom requires repair and which, when in need of same, may be repaired in the field.

Still another object is to provide such a device which is capable of cushioning very high loads and, more particularly, which has a load-cushioning capacity which will generally increase as the need for it increases.

Yet a further object is to provide such a device which does not substantially decrease the drilling efficiency of the string in which it is disposed.

These and other objects are accomplished, in accordance with the illustrated embodiments of the present invention, by a device in which a. plurality of pistons are so arranged as to provide successively effective forces 0pposing the shock and vibration loads on the bit. More particularly, the pistons have pressure-responsive surfaces exposed to the mud column so that the force provided by each will increase in proportion to the pressure of the mud column. The cushioning pistons are carried by one of a pair of relatively movable tubular members which are adapted to be connected as a part of the drill string, and

a means is carried by the other tubular member for successively moving different pistons in directions opposed to their cushioning forces as such tubular members move relative to one another in response to a load on the bit. In accordance with the preferred embodiment of the invention, this relative movement between the members is rotational as well as vertical so that the device will cushion torsional as well as axial loads on the bit and string.

The total pressure of the mud within the drill string includes the hydrostatic head of the mud column, the pressure drop across the bit at the lower end of the drill string, and the pump pressure required for circulating the mud up the annulus within the Well. Although the total pressure of the mud outside of the drill string is less since it does not include the pressure dilferential across the bit, the total pressure in either case increases with depth. Thus, whether the pistons are exposed to well fluid within or outside of the drill string, the cushioning forces of the pistons will increase as the loads on the bit increase due to harder formations.

Also, since the cushion is provided by the pistons, rather than by a sleeve vulcanized between the relatively movable tubular members, the bottom hole temperature in the well does not limit use of the device as a practical matter. Furthermore, the useful life of the device, excluding repairs, is limited only by the fatigue in the metal parts which generally is a much less serious factor than is encountered in the fatigue of rubber parts. Still further, the pistons and other parts of this device may be repaired or replaced in the field and by relatively unskilled personnel.

The pistons are carried by one of the tubular members for movement within cylinder means having a low pressure zone on the ends of the pistons opposite their ends exposed to the fluid pressure within the wells, and normally within the drill string. In the preferred embodiment of the invention, each piston is slidable within a separate cylinder so that one piston and cylinder may fail without impairing the over-all operation of the device. That is, in the event of the failure of one such piston and cylinder to hold pressure, the device will remain operative except for the one increment of force provided by such piston. In the design of this device, there are suilicient pistons to provide at least a substantially smooth succession of cushioning forces, whereby the loss of one or possibly more will not seriously impair the desired function of the device.

In the drawings, wherein like reference characters are used throughout to designate like parts:

FIGS. 1A and 1B are longitudinal sectional views of the upper and lower ends, respectively, of a device constructed in accordance with one embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view of the device of FIGS. 1A and 13 as seen along broken line 2-2 of FIG. 1A;

FIG. 3 is another enlarged cross-sectional view of the device of FIGS. 1A and 1B but as seen along broken line 33 of FIG. 1A;

FIG. 4 is an elevational view, broken away in part, of one set of cylinders and pistons removed from the interior of the device of the prior figures;

FIGS. 5A and 5B are longitudinal sectional views of the upper and lower ends, respectively, of another embodiment of the device constructed in accordance with the present invention;

FIGS. 6A and 6B are longitudinal sectional views of the upper and lower ends, respectively, of still another embodiment of the device constructed in accordance with the present invention; and

FIG. 7 is a cross sectional view of the device of FIGS. 6A and 6B as seen along broken line 7-7 of FIG. 6A.

to one skilled in the art, the connections 12 and 14 on the" tubular members enable them to be connected as part of the-drillstring with the-pin connection 12 preferably being connected to the lower end of the bottomdrill collar" (not shown) or the bit sub (not shown) and the box connection 14 being connected to the bit (not shown).

he second tubular member 13 is made up of a lower sub llfihaving an'opening 19a through the box connection on-its lower endand an'upper sleeve or conduit 16 having its lower end received withina counterbore 17 at the upper end of the sub and'seated upona shoulder 18 within such counterbore. The upper end of sleeve 16 extends into an opening-19- through pin connection 12 at the upper end of the first tubular member 11 so as to provide a continuous bore through the device litas well as an annulus 20 between the first and second'mernbers thereof. This not only confines the flow of drilling mud from the drill string into the bit, but also stabilizes the tubular members against wobbling out of axial alignment in the event one isloaded eccentricall'y of the other as will be described later.

The first tubular member 11 is made up of lower sub- 22 'threadedly connected at 23 to an upper sub 24 upon which the pin: connection 12 is formed. The lower end of sub 22 is slidablyreceived about the sub 150i the second tubular member, and the first and second tubularmembersareconnected to one another by means of spline 21 on sub 15 which interfits with spline 21a on subZZ of tubular member 11 as shown in FIG. 1B. Thus, the tubular members will move in-a-rotational direction with respect to one another in response to longitudinal or axial movement between the bit and drill string above thedevice. Conversely, the tubular members will move in alongitudinal or axial direction relative to one another in response to relative rotational movement between the bit and drill string above the device. Thus, as will be apparent from the descripti on to follow, the device is operable to cushion purely compressive loads onthe bit, purely torsion-a1 loads thereon, and a combination of the two loads.

As shown inPlG. 1A, a pair of annularcartridges 26- within each cylinder 27' between the supportedposition thereof shown in FIGS 1A and- 4 and anelevated position to be described hereinafter.

The lower cartridge-26 is supported on a shoulder on the-upper end of sub- 22, andthe upper cartridge 26 is supported above the lower cartridge by means of a spacer ring Zlcarried with-in the annulus and about the pistons 28 in the cylinders of the lower cartridge. The upper end of upper cartridge 26 abutts against: a downwardly facing shoulder 39011 upper sub 24 of first tubularmem-ber 11. Thus, as can be seen from FIG. 1A, there is considerable space between the upper ends of the pistons 28 of the lower cartridge and the lower end' of the upper cartridge as well as between the upper endsrof the pistons of the upper cartridge and the downwardly facing shoulder 31 on the sub Ztabout the opening 19through the upper end thereof.

In the assembly of the device, and with lower sub 22 removed from upper sub 24, the upper cartridge 26 with the pistons 28 supported Within cylinders. 27 is first moved into place to abut with shoulder se; the spacer 29 is moved into engagement with the lower end of the upper cartridge; and the lower cartridge with the pistons in place Within the cylinders thereof is then moved into engagement with the lower end of spacer 29. At this time, the lower sub 22 of tubular member 11 is threadedly connected .at 23 to the upper sub 24 so as to move the shoulder 25 into engagement with the lower end of the lower cartridge 26 and thus hold both cartridges finmly in place within the annulus 2%).

As can be. seen from FIGS. 1A and 1B,. the sleeve 16 has successively smaller diameter portions 16a, 16b, 16c and 1651 in a direction from its lower to its upper end. The lower portion 16a of greatest diameter fits within the counterbore 17 of sub 15 and is sealed with respect thereto by means of a pair of O-rings 32 or the like The upper end of the next largest diameter portion 16!) extends into the inner carried about the counte-rbore.

diameter of the lower cartridge 26- and' is sealed with respect thereto by means of another pair of Orings 33 or the like carried about the cartridge. The-succeedingly smaller diameter portion 1&0 of the sleeve 16 extends into the bore of the upper cartridge-2d, and the smallest diameter-portion 16:! at the upper end of thesleeve extends into opening 19 in the :pin connection 12 at the upper end of the device. As shown in FIG. 1A, an O-ring-33a surrounds the lower cartridge for sealing with sub 24- and, in cooperation with seal'rings32 and 33, sealably encloses the bore through the device from the exterior thereof.

As will be apparent from the foregoing description, there is an annular shoulder 34 about sleeve 16 intermediate theportions 16b and 16c thereof, and there is another annular shoulder 35 about such sleeve'between the portions and 16d thereof. The upper shoulder 35 is disposed just beneath a ring 35 carried about the sleeve portion 16d, and the lower shoulder 3d is carried some distance beneath a ring 37 carried about the sleeve portion led. As shown in FIG. 2, the ring 36 extends between the sleeve portion it surrounds and the inner diameter of the upper sub 24 of the first tubular member 11 and has recesses 33- formed on its outer circumference for receiving upwardly extending portions of the pistons 23 carried within the cylinders 27 of the upper cartridge. Although not shown in detail, the ring 37- also extends from surrounding; relation about the sleeve portion 16s to the enlarged inner diameter portion of the sub 24 and has recesses 39 formed in its periphery to receive upwardly extending portions of the pistons carried in the cylinders ofthe lower cartridge. More particularly, and as best shown in FIGS. 1A and 2, there are enlarged heads 40 on the upper ends of pistons 28 which provide downwardly facing annular shoulders 11 engageable by rings 36 and 37 therebeneath upon upward movement of the rings relative to the pistons. As shown in FIGS. 1A and 4, the enlarged heads 46 on the pistons carried by each cartridge are of different length and provide shoulders 41 which are staggered in a longitudinal direction so as to be successively engagedby ring 36' or 37, disposed there'beneath. In a prefered' form of-the invention the pistons are so arranged within each cartridge as to dispose successively engaged pairs of shoulders 41 at least approximately diametrically opposed to one another. Thus, for example and with reference to FIGS. 1A and 4, the shoulder of the rightmost piston of theupper cartridge will be the first and the shoulder of the leftmost piston Will be the secondto-be engaged by ring 36. Then, the shoulder for the center piston shown in 'FIG. 4 maybe the third to be engaged, and the diametrically opposed piston may be the fourth to be engaged, etc; In this manner, the

loads on the-device are at least approximately balanced wardly with respect to first tubular member 11. More particularly, the upper end of ring 36 is spaced from uppermost shoulder 41 thereabove a distance which is somewhat less than the spacing between shoulder 34 and the lower side of ring 37. Thus, upon upward movement of the second tubular member with respect to the first, ring 36 will successively engage different ones of pistons 28 carried by the first cartridge before ring 37 will engage any of the pistons carried by lower cartridge 26. However, upon continued upward movement of the second tubular member relative to the first, shoulder 34 will engage with the lower side of ring 37 and move such ring upwardly so it successively engages shoulders 41 on different ones of pistons 28 carried by the lower cartridge.

Alternatively, of course, shoulders 34 and 35 could be so arranged as to lift rings 36 and 37 simultaneously or at least in such a sequence as to cause the pistons of the two cartridges to be engaged alternateil. That is, for example, a piston of the upper cartridge could be the first to be engaged; a piston of the lower cartridge, the second to be engaged; etc.

As shown in FIGS. 1A, 1B and 4, each piston 28 carries a pair of O-rings 42 for sealing engagement with its cylinder 27. The lower end of each such cylinder is closed by means of a plug 43 so as to provide a low pressure zone 44 on the lower end of each piston 28. In the assembly of each cartridge, the pistons are first moved into the reccsses of rings 36 and 37 and the lower ends of the thusly mounted pistons are slidably moved into cylinders 27 (the plugs being removed therefrom). When the pistons are moved into engagement with the lower ends of the cylinders, plugs 43 are moved into place so as to enclose zone 44 at substantially atmospheric pressure.

There are ports 45 and 46 in sleeve portions 16d and 160 for communicating with annulus 20 above each of cylinder cartridges 26, Thus, the drilling mud within the bore of the device has free access into the annulus for acting across the upper ends of each of pistons 28. As

ell known in the art, the pressure of this mud, which includes the hydrostatic head of the mud column, the pressure drop across the drill bit, as well as the annulus circulating pressure of the mud pumps, is quite high, especially in deep wells where the harder formations are encountered. As a consequence, there is a large force acting upon the upper end of each piston 28 to hold it downwardly on the lower end of its cylinder 27 which in turn is carried by lower sub 22 of the first tubular member 11. Thus, as previously described, these pistons provide individual forces opposing upward movement of second tubular member 13 relative to the first and thus the loads, both torsional and longitudinal, imposed upon the bit. More particularly, due to the staggering of shoulders 41 on the upper ends or" these pistons, the forces provided thereby are successively effective as the second tubular member moves relatively to the first under the influence of the loads.

As an example of the cushioning forces which are thus available, it may be assumed the device is disposed in a well approximately 10,000 feet deep and the density of the mud within the well is 10.9 pounds per gallon. In such a case, the hydrostatic head of the mud column at the lower end of the drill string is 5,650 pounds per square inch. It is also reasonable to assume that under ordinary circumstances the pressure drop across the drill bit would be approximately 500 psi. and that the pump pressure for circulating the mud within the annulus would be approximately 300 p.s.i. so that the total fluid pressure acting on the upper end of each piston would be approximately 6,540 psi Thus, assuming the pressure in the low pressure zone is negligible and each piston has an area across seals 42 of approximately square inch, the total force actingdownwardly on each piston would be approximately 5,000 pounds. As will be apparent from the drawings, there are a total of 24 pistons so 6 the total capacity of the pistons of the device would be approximately 120,000 pounds at this depth.

Another force acting downwardly upon second tubular member 13 so as to cushion the loads on the bit results from the pressure drop across the bit which is effective on the annular area of lower sub 22 defined between the opening 19a therethrough and the inner diameter of counterbore 17. Assuming this annular area is five square inches, the total additional cushioning force would be approximately 2,500 pounds. This added force, although small in comparison with the accumulated forces of the pistons, would be effective to cushion the initial load upon the bit so the piston in position to first be moved by relative movement between the tubular members would be so moved only in response to approximately 7,500 pounds in load upon the bit.

That is, assuming that during operation of the drill string at the depth above described, and under the pressure conditions set forth therein, the load on the bit was 7,500 pounds, either by way of torsion, longitudinal load, or a combination of the two, second tubular member 13 would be urged upwardly to cause ring 36 to engage with lowermost shoulder 41 on one of the pistons of the set of pistons in upper cartridge 26. As the load on the piston increased above this value, however, the opposing force of the one piston would be overcome so the second tubular member would move upwardly to lift the first piston within its cylinder until ring 36 engaged with the second of the pistons so as to absorb the shock on the bit with a total force of approximately 12,500 pounds. Similarly, as the load on the bit rose above the 12,500 pound value, the second tubular member would move upwardiy another increment so as to lift the second piston along with the first and cause ring 36 to abut with the shoulder 41 on the third piston. Obviously, as the load on the bit decreased below the 12,500 pound figure, the accumulated cushioning forcesi.e., approximately 17,500 pounds-would cause ring 36 and second tubular member 13 to move downwardly so as to permit the third piston to seat.

As previously mentioned, the failure of one piston and cylinder, or for that matter more than one such piston and cylinder, does not render the entire device inopera tive. Thus, since the cylinders are separate of one another, the failure of the piston to seal within one of them will merely eliminate that increment of the total force of which the device is capable. That is, in the cushioning of a load on the bit, the second tubular member would be movable upwardly from the piston preceding the faulty one to the piston succeeding same so that the continuity of the successive forces would be retained.

In the interest of keeping these failures to a minimum, each piston 28 is surrounded by a sealing member 47 carried within the cylinder above the sealing engagement of the O-rings 42 therewith. Also, there is a passageway 48 through each piston connecting its upper end with the bore of the cylinder intermediate the O-rings 42 and sealing member 47. This passageway is packed with a grease or other suitable lubricant so that during the reciprocation of the piston within the cylinder such lubricant will be disposed between the relatively slidable surfaces of the piston and cylinder. Thus, in effect, the lubricant replaces the drilling mud which might otherwise find its way between the slidable surfaces of the pistons and cylinders and which, as well known in the art, is quite abrasive and known to score sliding surfaces.

As best shown in FIG. 1B, the lower end of spline 21 of sub 15 of the second tubular member provides a downwardly facing shoulder 49 which seats upon a bumper ring 50 carried within the lower end of sub 22 of first tubular member 11. More particularly, ring 50 is supported upon upwardly facing shoulder 51 of a split nut 52 threadedly connected to the main body of sub 22 and forming the lower end thereof. Thus, in the assembly of the device, spline 21 on the second tubular member is interfitted with spline 21a of the first tubular member, bumper ring 54) is moved into place, and nut 52 is threadedly engaged with the main body of sub 22 so as to support the bumper ring and thus spline 21 in operative position with respect to the spline of the first tubular member.

As shown in FIGS. 1A and 1B, the second tubular member is suspended from the first tubular member in a relaxed or unloaded position of the bit. However, as previously described, and in response to loading the bit, the second tubular member will be caused to move concurrently upwardly and rotatably with respect to the first tubular member which, of course, brings the cushioning pistonsabove described into play in the manner described. Assuming, however, that the total capacity of the device was exceeded, or even that all of the pistons and cylinders failed, the second tubular member would nevertheless be limited in its upward movement to retain the tubular members in force-transmitting relation. Thus, in this event, upper end 53 of spline portion 21 of sub would engage with a downwardly facing shoulder 56 on sub 22 of the first tubular member prior to disengagement of splines 21 and 21a. As will be noted from a comparison of FIGS. 1A and 1B, this distance is greater than the vertical spacing between shoulder 34 and ring 37 plus the vertical spacing between the upper side of ring 37 and uppermost shoulder 41 on the pistons of lower cartridge 26 so the movement of the second tubular member relative to the first is not limited until all of the pistons have had an opportunity to become effective.

As shown in FIG. 1B, there is a port 57 in sub 22 of the first tubular member connecting the lower end of annulus beneath lower cartridge 26 with the exterior of the device. This, of course, equalizes the pressure across the device beneath cartridges 26 so as to facilitate reciprocation of the splined portion of sub 15 within the lower end of annulus 21 during operation of the device.

The embodiment of the device shown in FIGS. 5A and 5B, and designated in its entirety by reference character 60, is. similar to device 10 described above in that it constitutes in effect a reversal of the parts thereof. Thus, afirst tubular member 61 having a pin connection 62.. about an. opening 63 in its upper end has a lower end telescopically slidable within a second tubular member 64 having a box connection 65 about an opening 66 through its lower end. As in the case of the device. of FIGS. 1A, 1B and 2 to 4, pin connection 62 is adapted to be threadedly connected. to the lower end of the lowermost drill collar or the bit sub of the drill string, and box connection 65 is. adapted to receive the pin connection of the bit whereby tubular members 61 and 64 may be connected as a part of the drill string.

The first tubular member (ill includes an upper sub 67 having pin connection 62 thereon and a sleeve 67a having its upper end received within a counterbore 68 on. the

low-er end of the sub. As will be apparent from FIGS.-

5A and SE, a bore 69' through sleeve 67 forms acontinuation of opening 63 through the upper end of sub- 67 and pin connection 62. Seal rings 7b are carried within the counterbore of the sub for sealing with respect to the outer diameter of sleeve 67a.

Second tubular member 64- includes a lower sub 71 having. box connection 65 and opening 66 therein and arr-upwardly extending sleeve 72 threadedly connected at 72a about the upper end of sub 71' and extending upwardly about a reduced outer diameter portion 73 of sub 67 of the first tubular member 61. As in thecase of device 10, there are spiral splines 74 on sub 67 of first tubular member 61 for interfitting with spiral splines 75 on sleeve 72' of second tubular member 64 so that, upon relative movement of the bit on the lower end of the device with respect to the drill string above the device, the second tubular member 64" will be caused to move upwardly and rotatably with respect to the first tubular member as defined by the lead of the splines.

Second tubular member 64 is suspended from the first in the inactive position of device 60' shown in FIGS. 5A and 55 by means of a split ring 76' threadedly connected to the upper end of sleeve 72 and resting at its lower end upon the upper end of spline 74 about sub 67. The up.- Ward movement of the second tubular member relative to the first is limited by the engagement of the topv end 77 of the split ring with a downwardly facing shoulder 78 about sub 67 above its reduced diameter portion 73'.

As shown in FIG. 5B, the lower end of sleeve 67a of first tubular member 61 extends downwardly through sleeve 72 of second tubular member 64 to provide. an annulus '79 therebetween as well as to provide acontinuous bore connecting openings 63 and 66 at the upper and lower ends of the device. Thus, the lower end of sleeve 67a fits closely within a counter-bore 80 insub 71 above opening 66 therein. Ports 8 1 within sleeve 67:: connect bore 69 therethrough with annulus 7 9 so drilling mud within the bore of the device as well as within the bore of. the drill string in which the device is connected has access to the annulus.

The first tubular member is. sealed with respect. to. the second tubular member during relative movement therebetween by means of seal rings 82 carried by inwardly enlarged portion of the sub 72 for sealing about sleeve 67a intermediate annulus 79 and the splines on they first and second tubular members. More particularly, a seal ring 83a is carried by lower sub 71 of the second tubular member for sealing with respect to the lower end of sleeve 72 so as to cooperate with seal rings 82 in containing well fluid within the device for communication with. annulus 75 In this embodiment of the invention, cylinders 83 formed in the lower end of the enlarged or thickened portion of sleeve 72 of second tubular member 64. are arranged in spaced apart relation concentrically of the tubular members. More particularly, and as shown in FIG. 5A, a piston 84 received in each cylinder carries a plurality of O-rings 85 thereabout for sealably sliding within the cylinder; and there is a port or passageway 86 extending through the length of each cylinder to facilitate assembly of the pistons within the cylinders. When this has been accomplished, plugs 87 are inserted into the lower ends of passageways 86 so as to contain substantially atmospheric pressure on ends $8 of the pistons at the closed ends of cylinders 83. As in the case of the pistons of device 10, the opposite ends of the pistons are exposed to the well fluid pressure which has access to annulus 79 to ward which these ends extend. Thus, this well fluid pressure is efiective to urge the pistons upwardly into seated positions against the upper ends of cylinders 83.

As was also the case of the pistons of device 10, pistons 84 have heads 89 on their ends to provide annular shoulders 9t) facing the cylinders and positioned for engagement with respect to a ring 91 carried by sleeve. 67a of first tubular member 61. In device 60, however, this en agement results from upward movement of. the second tubular member upon which the cylinder and pistons are carried relative to the first tubular member upon which the ring is carried. More particularly, thering has radially extending recesses 92 about its outer circumference so as to receive reduced diameter portions of the piston between heads 89 and the portions of the piston sealably slidable within the cylinders. Thus, the ring extends outwardly to substantially the outer diameter of annulus 79 so shoulder on each piston will have a large area of engagement with ring 91.

In the assembly of device 60, and. prior to making up sub 71 with sleeve 72, the reduced'portions of the several pistons 84 are first moved radially into positions within recesses 92 about ring 91. Sleeve 67a on which the ring is mounted together with the thusly assembled pistons 84 are then moved into sleeve 72 and cylinders 83, respectively. When the upper end of sleeve 67a abuts with the end of enlarged inner diameter portion of the lower end of sub 67 as shown in FIG. A, the pistons will have been fully inserted into the cylinders; and sub '71 can then be threaded to sleeve 72 so as to complete the assembly of the device.

As was the case of the pistons of the earlier device 10, the shoulders 90 on pistons 84 are staggered in a direction longitudinally of the device so the shoulders on diiferent ones of the pistons are spaced different distances from the lower side of ring 91. In this manner, therefore, as the second tubular member moves longitudinally upwardly in response to loads on the bit, shoulders 91 of different pistons will successive-1y engage ring 91 so such load is opposed by the increments of force provided by each such piston. That is, since pistons 84 are carried by the second tubular member which is connected to the bit, the opposing forces provided by the pistons will be effective in a downward direction so as to oppose the loading on the bit.-

Although device 60 is shown to have only one set of pistons, it obviously may have another, as in device 10, if greater cushioning capacity is desired. In fact, each of devices and 60 may have three or more sets of pistons in order to multiply its capacity to a desired extent. $1150, in the preferred form-of this device as inthe preferred form of-device 10, the shoulders of diametrically arranged pairs of' pistons are arranged for successive engagement with thering so as to reduce the eccentricloading on the .device to aminimum. Of course, any eccentricity in this respect is resisted by the sliding of the lower end of sleeve 67a within counterbore 86.

As was also the case in the earlier device 10, the splines 74 and 75 on the first and second tubular members make device 60 responsive to torsional as well as compressive loads on the bit in that each or a combination of the two loads causes a vertical :upward movement of the second tubular member relative to the first. Also, the distance between top side 77 of split ring 76 and stop shoulder 73 on the firsttubular member is greater than the distance between the lower side of ring 91 and piston shoulder 90 farthest from ring 91 so all the pistons are effective during operation of the device prior to the engagement of the limit shoulders. On the other hand, assuming the pistons and cylinders should fail and become ineffective to oppose the loads on the bit, these stop shoulders provide a means for continuing to transmit force between the drill string and bit.

In the device of FIGS. 6A, 6B and 7, which is designated in its entirety by reference character 1110, there is also a first tubular member 101 having a pin connectio 102 on its upper end and a lower end t lescopically slidable about a second tubular member 1133 having a connecting means (not shown) at its lower end. Thus, as in the previously described devices,.the pin is adapted for connection to the lower end of the lowermost collar or the bit sub of the drill string; and the connecting means .on the lower end of the second tubular member 1113 is adapted for connection to the bit whereby the device is connected as a part of the drill string.

First tubular member 1131 includes an upper sub 1115 having an opening 106 through pin connection 102 and an enlarged diameter portion below opening 166. The lower end of the enlarged diameter portion of sub 105 is threadedly connected at 167 to the upper end of a lower sub 1513 of the first tubular member. Similarly to the second tubular member of device 10, tubular member 103 in cludes a lower sub 109 having a counterbore 1111 at its upper end to receive the lower end of a sleeve 111 having va bore 112 therethrough (FIG. 6A) and extending within the enlarged diameter portion of sub 105 to form an annulus 113 therein. More particularly, the upper end of sleeve 111 extends into opening 106 through pin con- .nection 102 so as to provide a continuous bore between opening 166 and opening 114 through sub 109 at the lower end of the device. v

There are spiral splines 114a about the upper end of sub 109 for interengagement with splines 115 on the lower end of sub 108 so the tubular members are caused to move rotatably as well as axially of one another responsive to loading of the bit. More particularly, and as again was the case of device 10, the lower end of spline 114a seats upon a bumper ring 116 carried within sub 1118 by means of a nut 117 threadedly connected into the main body of the lower end of sub 108 as shown in FIG. 6B. In this manner, of course, the second tubular memher is suspended from the first tubular member in the inactive position of the device as shown in FIGS. 6A and 6B.

On the other hand, upward movement of the second tubular member relative to the first is limited by the engagement of the upper end of spline 114a with a downwardly facing shoulder 118 on the inner diameter of sub 108. This distance is, of course, greater than the effective travel of the force providing pistons to be described so the shoulders will engage only in the event of a failure of the pistons or in the event the loads upon the bit exceed the capacity of the device. Also, of course, this distance is less than the interengagement between splines 114 and 115 so as to maintain a force transmitting relation between the tubular members at all stages of the operation of the device.

In device 1%, annulus 113 is divided into upper and lower chambers by means of a ring 119 threadedly connected within sub 1115 and carrying a seal ring 120 for sealing about sleeve 111 as the latter moves therethrough during relative reciprocation of the first and second tubular members. The upper chamber between ring 119 and the upper end of the enlarged portion of sub 105 provides a cylinder which receives a series of pistons 121. More particularly, the pistons are annular in shape and arranged concentrically of one another for relative longitudinal sliding within the cylinder.

As shown in FIGS. 6A and 7, the lower end of pistons 121 are supported on ring 119 with their upper ends a substantial distance from the upper end of the cylinder. In this manner and as will be described to follow, in the inactive position of the device, the pistons are carried by the first tubular member in position to be moved by a part on the sleeve of the second tubular member as such second tubular member moves upwardly relative to the first one responsive to loads on the bit.

As shown in FIG. 6A, there are seal rings 124 between adjacent pistons as well as between the innermost and outermost pistons and sleeve 111 and sub 105, respectively, so as to separate the cylinder into a low pressure zone below the pistons and a high pressure zone above them. There is a port 126 in sleeve 111 above the upper ends of the cylinders so well fluid has access from the bore of the device into the high pressure zone of the annulus. Thus, as in the case of the pistons of device 11 pistons 121 are urged downwardly by the force of this well fluid. Also, of course, and as in the other devices, the lower ends of the pistons are exposed to relatively low pressure inasmuch as the pistons are assembled in the cylinder under atmospheric conditions.

As can be seen from FIG. 6A, the pistons are of diflerent length and there is an inwardly extending flange 122 providing a downwardly facing annular shoulder on the upper end of each piston. The lowermost flange on the innermost piston is disposed above a shoulder 123 about sleeve 111 while each of the other flanges is disposed in spaced relation above the upper end of the piston about which it is disposed. Thus, the shoulders are staggered in a direction longitudinally of the device so that different ones of them are successively moved upwardly by shoulder 123 as the second tubular member moves upwardly with respect to the first tubular member. That is, upon loading of the bit, shoulder 123 is moved upwardly to engage flange 122 of the innermost piston 121. When the load exceeds the cushioning force provided by this piston plus the force due to pressure differential across the device, sleeve 111 and shoulder 123 thereon move upwardly 1 1 a further distance to cause the upper end of the innermost piston to engage the shoulder of the adjacent piston. Thus, when the load upon the device is of such magnitude to make all the pistons eifective, the upper ends of such pistons will be raised to the positions thereof shown by broken lines-inFlG. 6A.

This device has the advantage of a substantially balanced. loading of the force-applying pistons although it has the disadvantage of pistons which are interdependent upon one another so as to maintain a differential pressure across them. That is, in device 100, as distinguished from the two earlier devices described, there is a common cylinder in which the'pistons are slidable; and the failure of one piston within such cylinder will result in the failure of all such pistons.

As in the case ofv device 1%, there are one or more seal rings 125' carried bycounterbore lllltl of the lowest sub 199 of the second tubular member for sealing with respect to the lower end of sleeve ill of such member, this seal cooperating with piston seals 124 to prevent the escape of well fluid from within the device during its operation. The thusly enclosed lower chamber or" annulus 113 beneath ring l 'i9'is vented to the exterior of the device by means of an equalizing port 12? so the second tubular member is free to reciprocate within the ubul'ar member during operation of the device.

It is also contemplated that, in accordance with the present invention, a helical member could be carried by one of the tubular members in a manner to provide it witha low pressure side and an opposite side exposed to the pressure of thewell fluid. Assuming that such a member was progressively collapsible from one end to the other, it would provide in effect an infinite number of separate pistons successively engageable by appropriate means on the other tubular member. This would, of course, havethe advantage of a smooth transition betweenthe cushioning forces' provided by the pistons.

From the foregoing, it Will be seen that this invention is one well adapted toattain all of the ends and objects hereinabove set forth, together with other advantage which are obvious and which are inherent to the apparatus and'structure.

Itwill be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims,

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that'all' matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. A device for use in absorbing shock and dampening vibration upon a drill string and bit in the drilling of a well, comprising first and second tubular members movable relative to one another and having means thereon for connecting them as partof the drill string, means including a plurality of pistons on one oi said tubular members, and means on the other tubular member for successively moving. diiferent pistons upon movement of said tubular members in one directional sense relative to one another, each of said pistons having a pressur responsive surface-exposed to well fluid pressure so as to oppose its movement by said means on-tho other tubular member and thereby oppose the relative movement of said tubular members in said one directional sense,

2. A device of the character defined in claim 1 including means for limiting relative movement of the tubular members in said one directional sense after movement of all of said pistons.

3. A device of the character defined in claim 1 wherein said first mentioned means includes a plurality of i2 separate cylinders, and each piston is. disposed in one of said cylinders.

4. A device for use in absorbing shock and dampening vibration upon a drill string and bit in the drilling of a well, comprising first and second tubular members connected for guided movement relative to one another in opposite axial directions, means on the tubular members for connecting them as part of the drill string, means including a plurality of pistons carried by one of said tubular members, each of said pistons having a pressure-responsive surface exposed to well fluid pressure so as to oppose its movement in one direction, and means carried by the other tubular member for successively moving different pistons upon movement of said tubular members in one axial directional sense relative to one another.

5. A device for use in absorbing shock and dampening vibration upon a drill string and bit in the drilling of a Well, comprising first and second substantially coaxial tubular members connected for guided movement relative to one another in a rotational sense, means on the tubular members for connecting them as part ofthe-drill string, means including a plurality of pistons carried on one of said tubular members, each of said pistons hava pressure-responsive surface exposed to Well fluid pressure so as to oppose its movement in one direction, and means carried-on the other tubular member for successively moving different pistons in said one directio-nupon movement of said tubular members in one rotational sense relative to one another.

6. A devicefor use in absorbing shock and dampening vibration upon a drill string and bitin the drilling of a well, comprising first and second tubular members connected for guided axial and rotational movement relative to one another, means on the tubular members for connecting them as part of the drill string, means including a plurality of. pistons on said tubular members, eachof said pistons having a pressure-responsive surfaceexposed to well fluid pressure so as to oppose its movement in one direction, and means on the other tubular member for successively moving different pistons in said one direction upon axial and rotational movement of said tubular members in one directional sense relative to one another.

7. A device for use in absorbing shock and dampening vibration upon a drill string and bit in the drillingof a well, comprising first and second tubular members arranged for movement relative to one another in opposite directional senses, means sealing between the tubular members during such movement to enclose a bore theretl rough, means for connecting the tubular members as part of the drill string withthe bore therethrough forming a continuation of the drill string bore, means including a plurality of pistons carried by one of the tubular members, and means carried on the other tubular memher for successively moving different pistons during movement of the tubular members in one directional sens-e relative to one another, each of said pistons having a pressure-responsive surface exposed to fluid pressure within the bore through said members soas to oppose its movement by said means on the other tubular member and thereby oppose the relative movement of said tubular members in said one directional'sense.

8. A device for use in absorbing shock and dampening vibration upon a drill string and bit in the drilling of a well, comprising a first tubular member and a second tubular member suspended from and arranged concentrically of the first tubular member for movement in op posite directional senses relative to the first tubular member, means for connecting the tubular members as part of the drill string, means including a plurality of pistons on one of the tubular members, each of said pistons having a pressure-responsive surface exposed to well fluid pressure so as to oppose its movement in one'direction, and means on the other tubular member for successively moving different pistons in said one direction upon movement of said tubular members in one directional sense relative to one another.

9. A device of the character defined in claim 8, including means on the tubular members limiting relative movement thereof in said one directional sense after movement of said pistons.

10. A device for use in absorbing shock and dampening vibration upon a drill bit and drill string, comprising first and second tubular members arranged concentrically of one another for relative movement in opposite directional senses, means on the first and second tubular members for connecting them as part of the drill string, cylinder means having a plurality of pistons slidable therein and carried by one of said tubular members, each piston having one end exposed to low pressure in the cylinder means and the opposite end exposed to well fluid pressure so as to oppose its movement in one direction, and means carried on the other tubular member successively moving difierent pistons upon relative movement between the tubular members in one directional sense.

11. A device of the character defined in claim 10, wherein said cylinder means comprises an annular cylinder formed between the first and second tubular members, and said pistons are arranged concentrically of one another for relative sliding within said annular cylinder.

12. A device of the character defined in claim 10, wherein said cylinder means comprises a plurality of cylinders, one for each piston and spaced apart substantially concentrically of the tubular members.

13. A device for use in absorbing shock and dampening vibration upon a drill bit and drill string, comprising a first tubular member and a second tubular member arranged concentrically of and suspended from the first tubular member for movement relatively with respect thereto, means on the upper end of the first tubular member and lower end of the second tubular member for connecting them as part of the drill string, means including a plurality of pistons supported within one of said members, each piston having one end exposed to well fluid pressure and the opposite end thereof exposed to a lower pressure so as to oppose its movement in one direction,

means on the other tubular member successively moving different pistons in said one direction upon relative movement between said members in one directional sense.

1 A device for use in absorbing shock and dampening vibration upon a drill bit and drill string in the drilling of a well, comprising a first tubular member and a second tubular member suspended from the first tubular member and arranged telescopically thereof to provide a bore therethrough and an annulus thereinbetween, a spline connecting the tubular members for guided relative movement longitudinally of one another, means on said tubular members for limiting their movement relative to one another in opposite directional senses and sealing between them to enclose said annulus during said movement, means on the tubular members for connecting them as part of the drill string with the bore therethrough forming a continuation of the drill string bore, means including a plurality of pistons carried by one of the tubular members with each piston having a pressure-responsive surface exposed to the annulus, means on the other tubular member for successively moving different pistons to urge them in one direction upon relative movement of the members in one of said directional senses, and means connecting the bore with the annulus to admit fluid pressure within the bore to the pressure-responsive surfaces of said pistons so as to oppose their movement in said one direction and thereby oppose relative movement of said members in said one directional sense.

15. A device of the character defined in claim 14, wherein the upper end of the second tubular member is telescoped within the lower end of the first tubular member, and the pistons are supported on said first member.

16. A device of the character defined in claim 14, wherein the lower end of the first tubular member is telescoped within the upper end of the second tubular member and the pistons are supported on the second member.

17. A device of the character defined in claim 14, wherein the spline is spiralled.

No references cited.

BROUGHTON G. DURHAM, Primary Examiner. 

1. A DEVICE FOR USE IN ABSORBING SHOCK AND DAMPENING VIBRATION UPON A DRILL STRING AND BIT IN THE DRILLING OF A WELL, COMPRISING FIRST AND SECOND TUBULAR MEMBERS MOVABLE RELATIVE TO ONE ANOTHER AND HAVING MEANS THEREON FOR CONNECTING THEM AS PART OF THE DRILL STRING, MEANS INCLUDING A PLURALITY OF PISTONS ON ONE OF SAID TUBULAR MEMBERS, AND MEANS ON THE OTHER TUBULAR MEMBER FOR SUCCESSIVELY MOVING DIFFERENT PISTONS UPON MOVEMENT OF SAID TUBULAR MEMBERS IN ONE DIRECTIONAL SENSE RELATIVE TO ONE ANOTHER, EACH OF SAID PISTONS HAVING A PRESSURERESPONSIVE SURFACE EXPOSED TO WELL FLUID PRESSURE SO AS TO OPPOSE ITS MOVEMENT BY SAID MEANS ON THE OTHER TUBULAR MEMBER AND THEREBY OPPOSE THE RELATIVE MOVEMENT OF SAID TUBULAR MEMBERS IN SAID ONE DIRECTIONAL SENSE. 